51313-02416-Selective Application of Corrosion Resistant Alloys Mitigates Corrosion in pH-Modified Geothermal Fluids

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Product Number: 51313-02416-SG

ISBN: 02416 2013 CP

Author: Bill Amend

Publication Date: 2013

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The Kawerau geothermal power generating station in New Zealand uses pH modification to mitigate scaling in flashed brine piping and injection wells. After less than 2 years of operation significant metal loss was observed in various areas of the steel piping and pressure vessels. The metal loss was generally localized and most extreme in areas of high velocity and turbulence. Corrosion allowance was exceeded in as little as X months in localized areas.

While root cause analyses and planning for alterations to key areas of the process continued corrosion mitigation strategies that focused on localized use of corrosion resistant alloys were tested in localized areas of the plant piping and equipment. The strategies included localized application of:
• Stainless steel or NiCrMo weld metal overlays
• Application of stainless steel plates and platelets welded to corrosion-susceptible areas
• NiCrMo alloys applied by thermal spraying (high velocity arc spraying)

Based on the observed performance of the initial attempts at mitigation the mitigation methods were further refined and the application expanded to larger areas additional alloys were tested for resistance to corrosion and cracking and selected components were replaced in their entirety with full thickness superduplex stainless steel.

This paper describes the development application and performance of the mitigation methods that rely on localized use of corrosion resistant alloys including the advantages and limitations of each method.